A conventional semiconductor structure 200 includes a silicon substrate 210, an under bump metallurgy layer 220 and a solder ball 230 as illustrated in FIG. 1. The silicon substrate 210 comprises an aluminum pad 211 and a protection layer 212, the under bump metallurgy layer 220 electrically connects to the aluminum pad 211, and the solder ball 230 is formed on the under bump metallurgy layer 220. Under the ball shear test for the semiconductor structure 200, owing to the material difference between the aluminum pad 211, the under bump metallurgy layer 220 and the solder ball 230, an intermetallic interface obviously exists therefore becoming the most fragile part in the semiconductor structure 200, which likely results in separation of the under bump metallurgy layer 220 from the aluminum pad 211 or even worse in destruction of the aluminum pad 211 so that the yield rate in manufacturing the semiconductor structure 200 is substantially reduced.